In a data network, computing devices or nodes exchange data via data links. Network nodes may include hosts such as personal computers, phones, or servers, as well as networking hardware such as gateways, routers, network bridges, modems, wireless access points, networking cables, line drivers, switches, hubs, repeaters, or hybrid devices incorporating multiple functionalities. Connections between nodes may be established via cable media or wireless media. Information is typically formatted into packets of data prior to transmission. The packets are sent from one node to another and then reassembled at their destination.
Software-defined networking (SDN) is an approach to data networking that allows for the management of network traffic from a centralized control center, without the need to physically manipulate individual switches. SDN separates the control plane of the network, which makes decisions about where traffic is sent, from the data plane, which forwards traffic to the selected destination. Thus, a controller, or server application, sends rules for handling packets to a switch, or data plane device. The switch may request guidance from the controller as needed, and provide it with information about the traffic being handled. Controllers and switches communicate via an interface such as but not limited to the OpenFlow protocol of the Open Networking Foundation. The SDN approach provides the flexibility of altering network switch rules to suit changing needs of businesses and institutions.